Desenvolvimento de um coletor do tipo amidodiol para flotação de itabiritos dolomíticos

Abstract

The Iron Quadrangle (MG) presents great relevance in the Brazilian economy due to the extensive iron ore extraction activities conducted in the region. Siliceous itabirite, composed mainly of hematite and quartz, is the lithology traditionally concentrated via reverse cationic flotation. However, significant reserves of dolomitic Itabirite, composed of hematite, dolomite, and quartz, are found in the mineral province, being still considered a marginal resource even with an iron content between 35 and 39%. This is caused by technological difficulties in the processing of this resource. The high dolomite (CaMg(CO3)2) content directly affects the concentration stages, where the ions released by this mineral can cause imbalance in the system, leading to contamination of the concentrate. This work sought to develop a new selective collector from oleic acid and diethanolamine, aiming at the flotation of carbonates present in dolomitic itabirites. In the study, hematite, quartz, calcite, and dolomite samples were used, whose characterization by FRX and DRX demonstrated purities greater than 90%. The N,N-bis(2-hydroxyethyl)oleamide (BHOA) collector was synthesized and characterized by 1H and 13C NMR and ATR-FTIR spectra, confirming the structure of the surfactant molecule and proving the success of the synthesis. The evaluation of the reagent's interfacial action indicated a CMC of approximately 70 mg/L. Microflotation tests with pure minerals were carried out under different conditions, with the highest selectivity window found at pH 10, at a concentration of 50 mg/L. In this scenario, the floatability of dolomite and calcite reached 74.7% and 78.1%, whereas hematite and quartz did not float. Adsorption via ATR-FTIR and zeta potential confirmed the selective action of the collector, indicating an adsorption of a specific nature. Tests carried out with a mixture of minerals indicated that the collector still presents a selective action towards carbonates in the presence of ions from dolomite and calcite. The addition of corn starch depressant in the flotation of mixed minerals, however, led to the depression of carbonates along with hematite.